Backpack



FIG. 1 is a front perspective view of a backpack;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a right elevation view thereof;

FIG. 5 is a left elevation view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines in the drawings are for the purpose of illustrating portions of the backpack that form no part of the claim. 

CLAIM The ornamental design for a backpack, as shown and described. 